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arp: Convert ioctl(SIOCGARP) to RCU.
ioctl(SIOCGARP) holds rtnl_lock() to get netdev by __dev_get_by_name() and copy dev->name safely and calls neigh_lookup() later, which looks up a neighbour entry under RCU. Let's replace __dev_get_by_name() with dev_get_by_name_rcu() and strscpy() with netdev_copy_name() to avoid locking rtnl_lock(). Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com> Link: https://lore.kernel.org/r/20240430015813.71143-8-kuniyu@amazon.com Signed-off-by: Jakub Kicinski <kuba@kernel.org>
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@ -1003,11 +1003,15 @@ out_of_mem:
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* User level interface (ioctl)
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*/
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static struct net_device *arp_req_dev_by_name(struct net *net, struct arpreq *r)
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static struct net_device *arp_req_dev_by_name(struct net *net, struct arpreq *r,
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bool getarp)
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{
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struct net_device *dev;
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dev = __dev_get_by_name(net, r->arp_dev);
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if (getarp)
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dev = dev_get_by_name_rcu(net, r->arp_dev);
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else
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dev = __dev_get_by_name(net, r->arp_dev);
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if (!dev)
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return ERR_PTR(-ENODEV);
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@ -1028,7 +1032,7 @@ static struct net_device *arp_req_dev(struct net *net, struct arpreq *r)
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__be32 ip;
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if (r->arp_dev[0])
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return arp_req_dev_by_name(net, r);
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return arp_req_dev_by_name(net, r, false);
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if (r->arp_flags & ATF_PUBL)
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return NULL;
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@ -1166,7 +1170,7 @@ static int arp_req_get(struct net *net, struct arpreq *r)
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if (!r->arp_dev[0])
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return -ENODEV;
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dev = arp_req_dev_by_name(net, r);
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dev = arp_req_dev_by_name(net, r, true);
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if (IS_ERR(dev))
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return PTR_ERR(dev);
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@ -1188,7 +1192,7 @@ static int arp_req_get(struct net *net, struct arpreq *r)
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neigh_release(neigh);
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r->arp_ha.sa_family = dev->type;
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strscpy(r->arp_dev, dev->name, sizeof(r->arp_dev));
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netdev_copy_name(dev, r->arp_dev);
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return 0;
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}
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@ -1287,23 +1291,27 @@ int arp_ioctl(struct net *net, unsigned int cmd, void __user *arg)
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else if (*netmask && *netmask != htonl(0xFFFFFFFFUL))
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return -EINVAL;
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rtnl_lock();
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switch (cmd) {
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case SIOCDARP:
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rtnl_lock();
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err = arp_req_delete(net, &r);
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rtnl_unlock();
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break;
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case SIOCSARP:
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rtnl_lock();
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err = arp_req_set(net, &r);
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rtnl_unlock();
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break;
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case SIOCGARP:
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rcu_read_lock();
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err = arp_req_get(net, &r);
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rcu_read_unlock();
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if (!err && copy_to_user(arg, &r, sizeof(r)))
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err = -EFAULT;
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break;
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}
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rtnl_unlock();
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if (cmd == SIOCGARP && !err && copy_to_user(arg, &r, sizeof(r)))
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err = -EFAULT;
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return err;
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}
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